PHYSICAL SCIENCES Grade 12 TERM 3 RESOURCE PACK

[Pages:146]PHYSICAL SCIENCES Grade 12

TERM 3

RESOURCE

PACK

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Contents

Worksheets

3

Topic 10: Electric Circuits

4

Topic 11: Electrodynamics

17

Topic 12: Optical Phenomena and Properties of Matter

32

Topic 13: Electrochemistry

43

Topic 14: The Chemical Industry

63

Formal Experiment: Electric Circuits

75

Technical Instructions

76

Learner's Worksheet

79

Marking Guidelines

85

Assessments91

Topic 10: Electric Circuits

92

Topic 11: Electrodynamics

108

Topic 12: Optical Phenomena and Properties of Matter

119

Topic 13: Electrochemistry

131

Topic 14: The Chemical Industry

140

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WORKSHEETS

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RESOURCE PACK

TOPIC 10: Electric Circuits

WORKSHEET QUESTIONS

TOTAL: 62 MARKS

1. Learners conduct an investigation to determine the emf and internal resistance (r) of the battery. They set up a circuit as shown in the diagram below and measure the potential difference using the voltmeter for different currents in the circuit.

r

A

V

The results obtained are shown in the graph below.

Graph of potential difference versus current

1,5

Potential difference (V)

1,0

0,5

0

0

0,5

1,0

Current (A)

1.1 Use the graph to determine the emf of the battery.

(1)

1.2 Calculate the gradient of the graph.

(3)

1.3 What physical property is represented by the magnitude of the gradient of the graph?(2)

4Grade 12 Physical Sciences

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WORKSHEETS

TOPIC 10

TOPIC 10: ELECTRIC CIRCUITS

1.4 How does the voltmeter reading change as the ammeter reading increases? Write

down INCREASES, DECREASES or REMAINS UNCHANGED. Use the formula

emf = I(R + r) to explain the answer.

(3)

2. The battery in the following circuit has an emf of 24 V and an internal resistance of 1,5 .

S1

V1

V2

R

A

10

15

S2

R is a resistor with an unknown resistance. The light bulb has a resistance of 15 . The resistance of the switches, S1 and S2 , ammeter and conducting wires can be ignored.

2.1 State Ohm's law in words.

(3)

2.2 What is meant by the internal resistance of the battery?

(2)

2.3 Calculate the effective resistance of the 10 resistor and light bulb.

(3)

When the switch S1 is closed, the bulb converts 576 J of energy per minute.

2.4 Calculate the reading on the voltmeter V2 when the switch is closed.

(4)

2.5 Calculate the reading on the ammeter.

(3)

2.6 Determine the resistance of resistor R.

(4)

2.7 Briefly explain what will happen to the reading on voltmeter V1 when switch S2 is

opened.

(4)

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RESOURCE PACK

3. Learners conduct an investigation to verify Ohm's law. They measure the current through a conducting wire for different potential differences across its ends. The results obtained are shown in the graph below.

Current (A)

00,.99 00,.88 00,.77 00,.66 00,.55 00,.44 00,.33 00,.22 00,.11 00

00 1,.0

2,.0 3.,0 4,.0 5,.0 6,.0 7,.0 Potential difference (V)

3.1 Which one of the measured quantities is the dependent variable?

(1)

3.2 The graph deviates from Ohm's law at some point.

3.2.1 Write down the coordinates of the plotted point on the graph beyond which

Ohm's law is not obeyed

(2)

3.2.2 Give a possible reason for the deviation from Ohm's law as shown in the

graph. Assume that all measurements are correct.

(2)

3.3 Calculate the gradient of the graph for the section where Ohm's law is obeyed. Use

this to calculate the resistance of the conducting wire.

(4)

4. Three resistors, R1 , R2 and R3 , are connected to a battery, as shown in the circuit diagram below. The internal resistance of the battery is 0,3 . The resistance of R2 and R3 is equal. The resistance of R1 is half that of R2 . When both switches are open, the voltmeter across the battery reads 9 V.

9 V

S1

r

N

S2

0,3

V1

R1 =R

R2 =2R

R3 =2R

A

P

Q

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WORKSHEETS

TOPIC 10

TOPIC 10: ELECTRIC CIRCUITS

4.1 What is the emf of the battery? Give reason for the answer.

(2)

4.2 When switches S1 and S2 are closed, the reading on the ammeter is 3 A. Calculate the resistance of R1 .(5)

4.3 Switch S1 is now opened.

4.3.1 How will the resistance of the circuit change? Write down only INCREASES,

DECREASES or REMAINS THE SAME.

(1)

4.3.2 What effect will this have on the "lost volts"? Explain the answer.

(3)

5. The battery in the circuit below has an emf of 12 V and an internal resistance of 0,2 . The resistance of the connecting wires can be ignored.

15 I

0,2

V

12 V

9

8

I

2

5.1 Calculate the current through the battery.

(6)

5.2 How will the reading on the voltmeter be affected if the 9 resistor is removed and replaced with a conducting wire of negligible resistance? Explain the answer. (4)

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CONSOLIDATION QUESTIONS

TOTAL: 52 MARKS

1. 1.1In an experiment, learners use the circuit below to determine the internal resistance of a cell.

E r

V

The circuit consists of a cell of emf E and internal resistance r. A voltmeter is placed across a variable resistor which can be set to known values R.

The equation used by the learners is:

1 V

=

r ER

+

1 E

They obtain the graph below.

Graph of 1 versus 1

V

R

2,0

1,5

1 V

(V -1 )

1,0

0,5

00

1

2

3

4

5

1 ( -1 )

R

1.1.1 Write down a mathematical relationship for the slope of the graph.

(1)

Use the information in the graph and calculate the:

1.1.2 emf of the cell.

(2)

1.1.3 internal resistance of the cell.

(3)

8Grade 12 Physical Sciences

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